flask post 请求 ImmutableMultiDict([])

import requests

def create_users():
    data = {
          "userlist": [
            {
              "username": "zhangsan",
              "age": 18,
            },
            {
              "username": "zhangsan",
              "age": 18,
            }
          ]
		}
    headers = {"contentType": 'application/json'}
    url = 'http://127.0.0.1:5001/create/users'
    res = requests.post(url, json=data, headers=headers)
    print(res.text)

if __name__ == '__main__':
    send_sys_msg()

contentType: 'application/json',

print(request.json)
print(request.get_data())